In the United States alone, there are roughly 4 million miles of roads. What if, instead of becoming lined with potholes, those roadways were generating solar energy under our wheels? What if the 4,360 square miles of surface parking lots in the United States could also be put to good use collecting solar energy? It's a compelling idea and one that's quickly catching on.

Last month, we wrote about Solar Roadways, a modular paving system that uses solar panels instead of asphalt. The technology comes from entrepreneurs Scott and Julie Brusaw who turned to Indiegogo to expand the reach of their concept. Their goal: an ambitious $1 million.

Now, with 15 days left in their campaign, they have already reached nearly $2 million in funding, 195% of their funding goal, and are breaking Indiegogo records in the process. It's a huge success in, at the very least, convincing the public that solar roadways are a great idea. Here's the video that has convinced close to 45,000 people to help fund the expansion of the product:

And Solar Roadways isn't just a pet project for the entrepreneurial engineers. They have already received two phases of funding from the U.S. Federal Highway Administration for research and development and have gone through, according to them, pretty rigorous testing (the glass panels can withstand 250,000 pound trucks for example).

The firm calculates that it would be anywhere between 50% and 300% more expensive to use its tiles rather than asphalt to pave a roadway. According to one estimate, the cost to cover all of America's interstate highways would be $1 trillion. This doesn't seem a cost-efficient way to harvest solar energy. Another problem is how to keep the tiles clean: roads tend to get rather dirty. And then there is the question of durability and maintenance: stuffed with electronics, they may not survive for long, especially in unforgiving climates.

And the firm will have to do more than convince the Internet about the potential of Solar (freakin') Roadways. It will have to convince cash-strapped local governments that they're worth the investment.